Computed tomography angiography (CTA) is used to exclude significant atherosclerosis in the coronary arteries, cerebrovascular and peripheral vascular systems. Sequential improvements in computed tomography (CT) architecture and software have facilitated significant improvements in the diagnostic accuracy of CTA. For example, for CT coronary angiography (CTCA) these developments include an increased number of detector rows from 64 to 320, faster gantry rotation speeds (≦350 ms), robust ECG gating techniques, automatic optimal phase detecting software and arrhythmia rejection programs. The resultant improvements in temporal and contrast resolution have enabled routine evaluation of the coronary arterial tree down to vessel segments as small as 1.5 mm in diameter and the demonstration of minimal plaque size down to 0.5 mm in diameter. These technical advances have facilitated a high negative predictive value for CTCA in excluding significant arterial disease, based on clear visualization of a vessel segment normal in caliber, without evidence of intimal plaque causing a flow limiting lesion and containing a uniform high signal (HU) from the contrast enhanced lumen. Successful and comprehensive diagnostic CTA requires accurate measurement of vessel caliber down to vessel segments as small as 1 mm, and accurate measurement of the density of contrast media in these small caliber vessels. However, the recent improvements in CT technology have not resulted in improved spatial resolution. This is an important limitation in the detection and accurate characterization of arterial plaque particularly in the coronary arteries. In the U.S., more than 1 million people per annum present with a sudden cardiac event, the majority having no cardiac related symptoms beforehand. A significant number of these patients have “high risk” coronary plaque that is vulnerable to rupture and cause acute coronary artery occlusion. This plaque is multifocal, contains a large, predominantly lipid core, a thin fibrous cap and does not cause significant reduction in the cross sectional area of the vessel lumen prior to rupture. Patients in whom this high risk plaque is detected have a greater than 5% one year risk of acute coronary syndrome or sudden cardiac death. Therefore, accurate measurement of plaque composition is required both for risk stratification and for assessment of strategies that target amelioration or reversal of atherosclerosis. However, the current clinical gold standard for assessment of coronary arterial plaque is intravascular ultrasound (IVUS), an invasive and time consuming technique. Computed tomography is non-invasive, but current CT units use matrix reconstruction algorithms which lead to a reduction in contrast and CT number for smaller objects (vessels and intimal plaque).